'UI-related' is formed from the acronym 'UI' (short for 'user interface') combined with the English adjective-forming element 'related' (the past-participle adjective from the verb 'relate').

'UI' itself is a modern acronym created from 'user interface' (a compound of 'user' + 'interface'); 'user' is from Middle English (from Old French 'user' and Latin 'uti'/'uti-' related forms meaning 'to use'), and 'interface' was coined in the 20th century from 'inter-' (Latin for 'between') + 'face' (from Latin 'facies', meaning 'face' or 'surface'). The word 'related' comes from Latin 'relatus', past participle of 'referre' (re- + ferre, 'to bring/carry back'), via Old French and Middle English to form English 'relate' and its past participle/adjectival form 'related'.

Originally, components like 'interface' referred to a surface or boundary between things, and 'related' meant 'brought back' or 'connected by relation'; together in modern usage they specifically denote a connection to the user interface—i.e., something concerning the user-facing surface or interaction layer.