Adding to what tsuwm and of troy have said:

Locust, langouste, and lobster are all ultimately from the Latin locusta 'a marine shell-fish, lobster; locust'. The AHD has this to say etymologically: "Middle English lopster, lobstere, from Old English loppestre, alteration (perhaps influenced by loppe, lobbe, spider)". Latin locusta is thought to come from the PIE root *lek- in words for 'extremities' and 'to bend, flex, jump, leap, hop, fidget'. Our word leg from the Old Norse leggr is related; also Skt r.ks.ala 'ankle joint of ungulates' / 'Fußgelenk bei Huftieren' Pokorny 673.

Yiddish treyf means 'unkosher', e.g., pork is always treyf, but a nice brisket could be treyf is it came into contact with dairy food, and otherwise OK meat could be unkosher if it wasn't slaughtered properly or was shot or otherwise had punctured skin. The Yiddish word comes from the Hebrew word TRPhH 'animal torn by wild animals; animal with organic defect; ritually forbidden food' < TRPh 'to tear to pieces; rend, pluck', cf. Arabic tarafa 'it grazed' said of a camel. Locusts are indeed not treyf, but are the only insects I know of that aren't. I remember a funny note in Rashi's commentary on the Torah forbidden French Jews from eating escargot.