לאַטקעס is the Yiddish word used for the potato pancakes commonly and commemoratively eaten on Chanukah. Where does the word לאַטקעס come from originally? What exactly does it mean?
Etymonline gives it as from Russian латка, "pastry", which may have come eventually from Ancient Greek ἐλαία, "olive" (or maybe it means modern Greek ελαία, "olive". I'm not sure).
Etymonline seems to be essentially correct. Two other sources discussed in Balashon's article here describe the journey a little more explicitly:
Yiddish latke, from either Russian latka or Ukrainian oladka, both derived (I assume) from Old Russian оладья, olad'ya. This is then apparently derived from the Greek ελαδια, eladia, "olive-y things", ultimately from Greek elaia, "olive". The original intent, as I understand it, referred to cheese pancakes or fritters fried in olive oil. Matthew Goodman suggests (in the Forward article linked in the Balashon post) that as Jews migrated eastward into Ashkenazi Europe the preferred frying agent shifted from olive oil to schmaltz (chicken fat) and thus cheese pancakes became simple buckwheat or flour pancakes (what the Russian/Ukrainian words refer to now). As the potato was introduced to Europe in the 17th century, it was slowly adopted, becoming popular in the first half of the 19th century.
Derekh agav/An aside: eating cheese/dairy on Hanukkah is an old tradition to honour Judith, who in the midrashic tradition defeats Holofernes by feeding him salty cheese and slaking his thirst with wine (while in the Apocryphal version there is no cheese, just wine); see Noam Zion's comments here, with citations from the Rama and the Kol Bo re: cheese on Hanukkah.