crabyoudaoicibaDictYouDict[crab 词源字典]
crab: Crab the crustacean [OE] and crab the apple [14] may be two distinct words. The word for the sea creature has several continental relatives (such as German krebs and Dutch krabbe) which show it to have been of Germanic origin, and some of them, such as Old Norse krafla ‘scratch’ and Old High German krapho ‘hook’, suggest that the crab may have received its name on account of its claws.

The origins of crab the fruit are not so clear. Some would claim that it is simply a metaphorical extension of the animal crab, from a perceived connection between the proverbial perversity or cantankerousness of the crustacean (compare crabbed) and the sourness of the apple, but others have proposed a connection with Swedish dialect skrabba ‘wild apple’, noting that a form scrab was current in Scottish English from at least the 16th century.
=> crayfish[crab etymology, crab origin, 英语词源]
crab (n.1)youdaoicibaDictYouDict
crustacean, Old English crabba, from a general Germanic root (compare Dutch krab, Old High German krebiz, German Krabbe, Old Norse krabbi "crab"), related to Low German krabben, Dutch krabelen "to scratch, claw," from PIE root *gerbh- "to scratch, carve" (see carve). The constellation name is attested in English from c. 1000; the Crab Nebula (1840), however, is in Taurus, the result of the supernova of 1054, and is so called for its shape. French crabe (13c.) is from Germanic, probably Old Norse.
crab (n.2)youdaoicibaDictYouDict
"fruit of the wild apple tree," c. 1300, crabbe, perhaps from Scandinavian (compare Swedish krabbäpple), of obscure origin. The combination of "bad-tempered, combative" and "sour" in the two nouns crab naturally yielded a verb meaning of "to vex, irritate" (c. 1400), later "to complain irritably, find fault" (c. 1500). The noun meaning "sour person" is from 1570s.