'lopsidedly' originates from English, specifically formed from the adjective 'lopsided' plus the adverbial suffix '-ly', where '-ly' meant 'in the manner of' or 'having the quality of'.

'lopsided' itself developed in English by combining 'lop' (a root meaning to lean or hang to one side in some dialectal uses) + 'side' with the adjectival suffix '-ed'; later the adverb 'lopsidedly' was created by adding '-ly' to the adjective.

Initially it described a physical tilt or imbalance ('tilted to one side'), and over time it retained that sense while also gaining a figurative sense of 'biased or uneven in treatment'.