Oh well, do not ask me about nicknames... Every Pokémon has to have a nickname in my game! Mostly I give them names I like, in most cases it is just the name with no additional meaning or something. A great part do have something in common with the name of the Pokémon. That could be the first 1/2/3 characters of the name, maybe a particle of it, or a name which is hidden in the Pokémon name. But I do like names with a meaning, so a name with a meaning which is striking for the Pokémon could be applied too. Furthermore, the 'meaningful' names, which are no common names for people, but based on things, phenomena or thoughts, are another category. And what is left, are the funny names! Of course I do not like some Pokémon, so I will torment them with a weird nickname. And others just have bad luck. That category is not that relevant for people here, because they are mostly made out of jokes in my native language. And translating them would be dumb.
Let's explain some names, then!
Ambipom: Ambidexter (F/M)
Very funny for such an idiotic Pokémon like Ambipom. ^^
Roselia: Rosalie (F)
An 'anagram' for Roselia (although only two vowels are swapped), and well, just look at the name... It is almost the same, and it has something to do with roses.
Salamence: Salami (F/M)
Another name which is not that serious, but as you can see the first five letters are the same.
Lunatone: Luna (F)
About 'names in names', Luna is very striking for a Pokémon that looks like a moon!
Sandshrew/Sandslash: Sandra (F)
Instead of Wraith picking the 'shrew' part, I picked the 'sand' part and wait, Sandra contains the word sand! Plain and simple.
Nidorina: Rina (F)
I think I do not have to explain that name?
Kadabra: Kadaver (F/M)
Well, from the department of morbid humour, the name is derived from Cadaver, as you could notice.
Bellsprout/Weepingbell/Victreebel: Bella (F)
The whole evolutionary chain contains at least the letters 'bel', so...
Ponyta: Lavinia (F)
I really like that name, and somewhere it almost has 'lava' in it, so it looks suitable for a Fire Pokémon. But besides that, it is just a cute name for a Ponyta.
Muk: Musk (F/M)
A well-known ingredient of perfume, must smell a lot nicer than a Muk, according to the Pokédex!
Tangela: Angela (F)
The most extreme form of 'a name in a name', just remove the T and you get Angela.
Omastar: Stella (F)
This one is clear I suppose?
Moltres: Sulfura (F/M)
Sulfura is the French name of Moltres, derived from sulphur as it seems. Anyway, I like that name a lot better!
Dratini: Snoepje (F)
The diminutive of sweet or candy in Dutch, because Dratini is such a sweet thing. ^^
Meganium: Megan (F)
It is starting to get a bit boring with explaining...
Noctowl: Athena (F)
This one is as cliché as it can be, I am afraid.
Flaaffy: Morgana (F)
Yes, this one is a least thought-through. Morgana is the shepherdess from the opera Alcina of Georg Friedrich Händel (which is based on the epic of Ludovico Ariosto, named 'Orlando Furioso'). I am not really sure, but I thought Morgana did not belong to the epic of Ariosto, although the link between sheep and shepherdess is close enough, I think.
Sudowoodo: Sudoku (F/M)
Well, look at the similarity. A funny name for people who like those games.
Sunkern/Sunflora: Sunny (F)
The perfect Pokémon to be called Sunny, I think.
Wooper: Miyako (F)
I really like this name, but I only recently gave it to my Woopers/Quagsires. It comes from 'mi' (beautiful), 'ya' (night) and 'ko' (child). 'Ko' is often used for the end of female names, but the meaning of it is in this case fairly good for a little Wooper.
Mantine: Tamanta (F/M)
The romanised Japanese name, I believe. Tamana could also be used if you have a female Mantine.
Skarmory: Victoria (F)
I have the tendency to give birds the name Victoria (I used it for Fearow and Pidgeotto too, for example).
Tyranitar: Tyra (F)
Drop -nitar and you get this! I do not have Tyranitars often, though.
Lugia: Lucia (F)
One character change and you got a proper name.
Ho-oh: Aurelia (F)
For those who do not know; it means 'Dawn'.
Linoone: Angelina (F)
Especially the 'Lina' part comes from Linoone.
Kirlia: Kiri (F)
Named after the girl in Sootopolis City who gives you berries every day.
"My parents wished I would grow healthy and warm-hearted", or something like that.
Gardevoir: Cynthia (F)
Plusle: Kyrielle (F)
I listed this one because I have no clou where I found this weird name.
Torkoal: Etna (F)
Well, you could use another random volcano on earth for it.
Regirock: Ragnarok (F/M)
I cannot get enough of this: Ragnarok looks a lot like Regirock. It comes from the Norse mythology of course, the awaiting disastrous events in the future that destroy everything. Well, maybe a bit optimistic for Regirock's power, I guess. ^^
Regice: Antarctica (F/M)
Another 'meaningful' name of the same kind as the one above, but Antarctica is a very innocent name instead.
Infernape: Incendie (F)
Incendie means 'fire' in French.
Bronzong: Campanella (F/M)
Meaning 'little bell' in Italian, and I believe Bronzong is supposed to be a bell?
Snover: Setsuna/Suzuna (F)
I used both names, but Setsuna had something to do with snow ('calm snow', or something).
Togekiss: Valentina (F)
Named after my favourite classical pianist Valentina Lisitsa.
Gallade: Ballade (F/M)
Again, the secret of one character change! Together with Waltz (for Ralts), I would make a whole dance related evolutionary chain, but I cannot come up with a good dance which looks like Kirlia and Gardevoir.
Froslass: Candy (F)
Because Froslass looks like a candy, with that ribbon around her middle.
Uxie: Gyeonmun
I could not come up with a good name for it, something with acuity did not work too, so I switched to Korean. It seems to mean 'knowledge', but there is a chance I picked the wrong word.
Heatran: Lavana (F)
I thought one of the three minor leaders of team Dim Sun was called Lavana.