What's the "een" in Halloween?
c.1200, fift, from Old English fifta, from fif "five" (see five) + -ta (see -th (1)). Altered 14c. by influence of fourth. Cf. Old Frisian fifta, Old Saxon fifto, Old Norse fimmti, Dutch vijfde, Old High German fimfto, German fünfte, Gothic fimfta.
Noun meaning "fifth part of a gallon of liquor" is first recorded 1938, American English. Fifth Avenue (in New York City) has been used figuratively for "elegance, taste" since at least 1858. Fifth wheel "superfluous person or thing" first attested 1902. Fifth-monarchy-man, 17c. for "anrachist zealot," is a reference to Dan. ii:44.
Coming after fourth, as in order, rank, or time.
Being the outermost digit, as on a hand.
To refuse to testify in court on the basis of the protection of the Fifth Amendment of the US Constitution; to refuse to answer any questions: took the Fifth on every question