'frequency-related' originates from English compounding of 'frequency' and 'related'. 'frequency' ultimately comes from Latin 'frequentia', where 'frequens/frequent-' meant 'repeated' or 'crowded', and 'related' comes from Latin 'relatus' (past participle of 'referre'), where the prefix/root indicated 'carried/back' in the sense of 'brought into relation'.

'frequency' entered English via Middle French/Old French (e.g. 'frequence') from Latin 'frequentia' and developed into the modern English 'frequency'; 'related' is the past participle form of 'relate', from Old French/Latin roots (Latin 'referre' -> past participle 'relatus') and became the English 'related' as used in compound adjectives. The compound 'frequency-related' is a modern English formation combining these elements.

Initially, Latin 'frequentia' often implied 'crowding' or 'repetition'; over time this shifted to the modern senses of 'rate of occurrence' and, in physics/engineering contexts, 'cycles per unit time'. The component 'related' has remained as indicating connection or relevance, so the compound now means 'having a connection to frequency (rate or cycles)'.