The word 'yearly' is a transparent compound formed within English from its core native vocabulary. Its first element, 'year', descends from the Old English 'gear', a term of Germanic origin tracing back to the Proto-Indo-European root yēr-, which denoted a cycle of seasons or a period of time. The suffix '-ly', from Old English '-lic', originally created adjectives meaning "body-like" or "having the form of". By combining these elements, 'yearly' literally means "having the character or period of a year". This logical construction directly yields its modern senses, describing something that recurs with the regularity of the annual cycle or is performed in a manner measured by the year.

Structure: year (time period) + ly (adjective/adverb suffix) - year: From Old English 'gear', meaning a cycle of seasons, a year. Its ultimate origin is Proto-Germanic jǣram and Proto-Indo-European yēr-, meaning year, season. - ly: A suffix from Old English '-lic', used to form adjectives meaning "having the qualities of" or adverbs meaning "in a specified manner".