'micronucleus-bearing' is a compound formed from 'micronucleus' and 'bearing'. 'micronucleus' itself combines the Greek prefix 'micro-' (from Greek 'mikros') meaning 'small' and Latin 'nucleus' meaning 'kernel, core'; 'bearing' comes from Old English 'beran' meaning 'to carry'.

'micronucleus' was coined in scientific contexts by combining 'micro-' + 'nucleus' in modern (19th–20th century) biological terminology; 'bearing' developed from Old English 'beran' → Middle English 'beren' and into modern English 'bear' with the present participle 'bearing'. The compound form arose by joining the noun 'micronucleus' with the participial adjective 'bearing' to indicate possession.

Originally 'bear' meant 'to carry' in a general, often physical sense; in modern English, in compounds like 'micronucleus-bearing' it has the extended sense 'having' or 'possessing'. 'micronucleus' originally named a 'small nucleus' and retains that specific biological meaning.