'lag-free' is a Modern English compound formed from 'lag' + 'free'. 'lag' originates from early modern English, probably influenced by Scandinavian roots meaning 'to fall behind' or 'to be slow', while 'free' originates from Old English 'frēo' meaning 'not bound' or 'without restriction'.

'lag' developed in English to mean 'a falling behind' or 'delay', and 'free' long meant 'without' or 'not affected by'. In Modern English these two words were combined as a compound adjective 'lag-free' to describe systems or experiences without delay.

Initially, the separate words meant 'delay/being slow' (lag) and 'not affected' (free); together they evolved to the specific technical sense 'without perceptible delay' used especially for digital/video/audio and network contexts.