'unevenly-awned' originates from Modern English compounding of the adverb 'unevenly' and the past-participle/adjectival form 'awned' (from the noun 'awn', meaning a bristle or stiff hair on grasses).

'unevenly' is the adverbial form of 'uneven' (Middle English 'uneven', formed with prefix 'un-' + 'even'), and 'awned' is formed from 'awn' (Middle English attested forms such as 'aune') used as a past-participle/adjectival form; the compound itself is a modern descriptive formation.

Initially the components meant 'not even' + 'having awns'; combined, the compound's meaning is a straightforward descriptive extension: 'having awns in an uneven distribution' with little semantic shift from its parts.