'ill-stocked' originates from English, specifically a compound of the adjective 'ill' and the past-participle adjective 'stocked', where 'ill' originates from Old English 'yfel' meaning 'bad' and 'stocked' derives from the past participle of 'stock', which originates from Old English 'stocc' meaning 'tree trunk' or 'post' and later developed senses of 'supply' or 'goods'.

'stock' changed from Old English 'stocc' to Middle English 'stok'/'stock' (meaning a post or trunk and later supplies); the past participle form 'stocked' arose from the verb 'to stock'. 'ill' changed from Old English 'yfel' to modern 'ill'. The compound 'ill-stocked' was formed in Modern English by combining these elements to describe poor supply.

Initially the element 'stock' referred to a trunk or post and then to goods or supplies; combined with 'ill' the compound meant 'badly supplied' and over time this developed into the current sense of 'poorly supplied/insufficiently stocked'.