the compound adjective 'thin-lipped' is formed from two native english elements. the first element, 'thin', derives from old english 'þynne', meaning narrow or having little thickness, a concept with proto-germanic origins. the second element, 'lipped', originates from old english 'lippa' for 'lip', combined with the adjectival suffix '-ed' to denote possession of a specific kind of lip. the term's literal anatomical meaning evolved a figurative sense, where 'thin-lipped' describes a restrained, tight-lipped, or disapproving manner of speaking, metaphorically linking the physical trait to a characteristically tight or ungenerous expression.

Structure: thin (narrow) + lipped (having lips) thin (old english, meaning 'narrow or slender'); lipped (old english, from 'lippa' meaning 'lip', with the suffix '-ed' indicating 'having the quality of')