'scaled-tailed' is a modern English compound formed from the past participle 'scaled' (from the noun 'scale') and the past participle 'tailed' (from the noun 'tail'), created to describe an animal feature.

'scaled-tailed' developed directly in modern English by compounding two participial adjectives; it does not have a long separate historical lineage as a single lexical item.

The compound originally and still primarily describes an animal feature; over time its use has become a straightforward descriptive adjective meaning specifically 'having scales on the tail.'