'lean' originates from Old English, specifically the word 'hlēanian', where the root meant 'to incline, to bend'.

'hlēanian' changed into Middle English forms such as 'lenen'/'leanen' and later became the modern English verb 'lean'; the noun 'leaning' is derived from this verb with the -ing suffix and 'leanings' is its plural.

Initially it meant 'to incline or bend physically', and over time it kept that sense while also developing a figurative meaning 'to incline toward an opinion or preference', which led to the noun sense 'a tendency or preference'.