The plural of giraffe, according to Merriam Webster and some other dictionaries I checked, is "giraffes".
Normally when the final sound of an English word is F, its plural ends in V sound. But not always.
- knife → knives
- wife → wives
- life → lives
- wolf → wolves
- leaf → leaves.
But giraffe → giraffes?
My best guess would be that the former words are all native English words while "giraffe" is not.
I searched "wolf" in Etymology Dictionary and it says:
from Old English wulf
For "life" it says:
Old English life (dative lif)
For "wife" it says:
Middle English wif, wyf, from Old English wif
For "knife" it says:
late Old English cnif
BUT for "giraffe" the entry is quite different:
long-necked ruminant animal of Africa, 1590s, giraffa, from Italian giraffa, from Arabic zarafa, probably from an African language. Earlier Middle English spellings varied wildly, depending on the foreign source, and included jarraf, ziraph, and gerfauntz, some apparently directly from Arabic, the last reflecting some confusion with olifaunt "elephant.
The modern form of the English word is attested by c. 1600 and is via French girafe (13c.). Replaced earlier camelopard (from Latin camelopardalis), which was the basis form the name of the "giraffe" constellation Camelopardalis, among those added to the map 1590s by Flemish cartographer Petrus Plancius.
So why is the plural of giraffe different than the other similar words? Why is it not "giraves"?