A dime a dozen

[dahym] /daɪm/
noun
a cupr-nickel-clad coin of the u.s. and canada, the 10th part of a dollar, equal to 10 cents.
slang.

ten dollars.
a 10-year prison sentence.
dime bag.

idioms
a dime a dozen, informal. so abundant that the value has decreased; readily available.
dime
/daɪm/
noun
a coin of the us and canada, worth one tenth of a dollar or ten cents
a dime a dozen, very cheap or common
word origin
c14: from old french disme, from latin decimus tenth, from decem ten
dime
n.

chosen 1786 as name for u.s. 10 cent coin, from dime “a tenth, t-the” (late 14c.), from old french disme (modern french dîme) “a tenth part,” from latin decima (pars) “tenth (part),” from decem “ten” (see ten).

the verb meaning “to inform” (on someone) is 1960s, from the then-cost of a pay phone call. a dime a dozen “almost worthless” first recorded 1930. phrase stop on a dime attested by 1954 (a dime being the physically smallest unit of u.s. currency).
noun

a ten-year prison sentence (1960s+ underworld)
a thousand dollars, esp as a bet (1960s+ gambling)

verb

(also drop a dime) to inform on someone; sing, squeal: frankie would have been okay if somebody hadn’t dimed on him (1960s+ underworld & prison)
related terms

five-and-ten, get off the dime, nickel and dime, on someone’s dime, stop on a dime, a thin dime, turn on a dime

[verb sense from the dime dropped into the pay telephone for the call to the police]

dime