the adjective 'wary' entered english in the 16th century, derived from the now-obsolete verb 'ware', meaning 'to be cautious'. this verb itself came from the old english 'wær', meaning 'cautious, aware', which traces back to the proto-germanic 'waraz' (cautious, careful). this germanic root is connected to the proto-indo-European 'wer-' (to perceive, watch out for), a root also giving rise to words like 'aware', 'ward', and 'guard'. the '-ly' suffix is a common english adverbial ending from old english '-lice', related to the adjective suffix '-ly' meaning 'having the qualities of'. thus, 'warily' literally means 'in a cautious manner', preserving the core sense of watchful alertness from its ancient root.

the word is an adverb formed by adding the suffix '-ly' to the adjective 'wary'. it is not further segmented into meaningful morphemes in modern english spelling.