second hand vs intermediary

second hand and intermediary both are nouns.

Word	Noun	Adjective	Verb	Adverb
second hand	Yes	No	No	Yes
intermediary	Yes	No	No	No

As nouns, intermediary is a hypernym of second hand; that is, intermediary is a word with a broader meaning than second hand:

Other hypernyms of second hand include go-between, intercessor, intermediator, mediator.

second hand (noun)	intermediary (noun)
hand marking seconds on a timepiece	a negotiator who acts as a link between parties
an intermediate person; used in the phrase `at second hand'

second hand (adverb)	intermediary (adverb)
from a source of previously owned goods