The word 'irregularly-spread' is a compound formed from 'irregularly' (from 'irregular' + '-ly') and 'spread' (from Old English 'spredan'). 'Irregular' comes from Latin 'irregularis', where 'in-' means 'not' and 'regularis' means 'regular'.

'Irregularly' developed from 'irregular' in Middle English, and 'spread' from Old English 'spredan'. The compound 'irregularly-spread' is a modern English formation.

Initially, 'irregularly' meant 'in a manner not regular', and 'spread' meant 'to extend over a surface'. Together, 'irregularly-spread' came to mean 'spread in a non-uniform way'.