'baldy' is formed from English 'bald' + the adjectival/noun-forming suffix '-y', creating an informal noun/adjective meaning 'having a bald head'.

'bald' comes from Old English 'bald' (also spelled 'beald'), and the informal derivative 'baldy' emerged in later English (early modern to modern periods) as a colloquial way to refer to someone who is bald.

Originally 'bald' had senses related to 'white' or 'shining' and later came to mean 'without hair'; 'baldy' developed as an informal/colloquial form specifically referring to a bald person or describing baldness.