'irregularly-stocked' originates from English compounding, combining 'irregularly' and 'stocked'; 'irregularly' ultimately derives from Latin 'in-' meaning 'not' + 'regula' meaning 'rule' (via 'regular'), and 'stocked' is the past participle of 'stock', from Proto-Germanic '*stokkaz' meaning 'log, trunk'.

'irregularly-stocked' formed in Modern English by hyphenating the adverb 'irregularly' (from Middle English via Old French/Latin roots related to 'regular') with the participial adjective 'stocked' (from Old English 'stocc' > Middle English 'stok' > Modern English 'stock'), yielding the current compound adjective.

Initially, it meant 'stocked in an irregular manner', and this meaning has remained essentially the same in modern usage, especially in retail and inventory contexts.