The compound 'thirdhand' is a relatively modern English formation, built by combining the ordinal number 'third' with the noun 'hand'. The term follows the established pattern of 'secondhand', which originated in the 17th century to describe goods not acquired from the original maker or owner, metaphorically extending the sense of 'hand' from physical possession to a stage in a chain of transfer. 'Thirdhand' logically extends this sequence, denoting something that has passed through two intermediate stages or owners, moving further from the primary source. This compounding illustrates the English language's capacity for transparent, analogical word-formation to describe degrees of indirectness in both commerce and information.

Structure: third + hand - third: From Old English þridda, from Proto-Germanic þridjô, meaning "coming next after the second." Functions as a numerical root. - hand: From Old English hand, meaning "hand" or "possession." Functions as a noun root, here used metaphorically to indicate transmission or possession.