'semi-adjustable' originates from Modern English as a compound of the prefix 'semi-' and the adjective 'adjustable'. 'semi-' originates from Latin, specifically the word 'semis', where 'semis' meant 'half'. 'adjustable' traces back through Old French 'ajuster' to Latin elements such as the prefix 'ad-' and Latin 'juxta' (near).

'semi-' (from Latin 'semis') combined with the existing English adjective 'adjustable' (itself influenced by Old French 'ajuster' and Latin roots) to form the compound adjective 'semi-adjustable' in modern usage.

Initially the prefix 'semi-' meant 'half' and 'adjustable' meant 'able to be adjusted'; together they originally indicated 'half-adjustable' or 'partly able to be adjusted.' Over time this stabilized into the current sense 'partly adjustable' or 'adjustable to a limited extent.'