Last year, Rabbi Josh Waxman of Parshablog put up the following post on the etymology of sufganiyot סופגניה:
This is admittedly silly, and probably obvious to some, but what is the etymology of sufganiyot (jelly donuts eaten on Chanukka)?
The answer: from sponge, in that it is something which absorbs (oil, I guess). We see this root spg in Hebrew, and in the gemara - one of the more famous examples is sofeg et ha'arbaim, which means that he is lashed 40 (=39) times, that is, he absorbs the 40.
About sponge: According to the American Heritage Dictionary (cited at dictionary.com), the etymology is:
[Middle English, from Old English, from Latin spongia, from Greek spongia, from spongos.]
According to Easton's 1987 Bible dictionary (also cited at dictionary.com), the word
"occurs only in the narrative of the crucifixion (Matt. 27:48; Mark 15:36; John 19:29). It is ranked as a zoophyte. It is found attached to rocks at the bottom of the sea."
What about that n? Shouldn't it be spoge if it is the same root as sofeg? Well, in Greek, doubled gamma is pronounced ng. My favorite example of this is the word angel which is spelled gamma gamma rather than nu gamma.
Josh really covered it, but I have a few points to add:
a) Besides "sponge", spongos (or sphongos) is related to the English words fungus, spunk and punk.
b) Jastrow writes (in his entry for ספוג ) that spoggos "seems to be of Semitic origin", but this site claims that:
The Indo-European root for the fungus-spunk-punk-sphongos-sponge group of words is *panx, a root so very old that it is shared with Uralic, the otherwise unrelated language family of northern Eurasia. Since all the regular sound changes have occurred in both sets of daughter dialects, it is impossible to ascertain whether the loan word was from the Uralic to Indo-European, or vice versa.
c) While the double gamma (digamma) is also attested to here and here, I wonder if the Hebrew ספג wouldn't have been influenced by the tendency of Hebrew to "drop nuns".
d) Perhaps the precursor of the sufganiya was the sufgan סופגן - as found in the Mishna (Hallah 1:4) - also some kind of sponge cake.
e) And of course we can't forget the sufganiya's cousin: sponja ספונג'ה - washing the floor. This entered Hebrew via Ladino - espongar (to clean) with an esponja (a sponge.)