The story
- Proto-Indo-European*né
- Proto-Indo-European*n̥-
- Proto-Germanic*un-
- Proto-West Germanic*un-
- Old Englishun-
- Middle Englishun-
- Englishun-
- Proto-Indo-European*h₁én
- Proto-Italic*en
- Proto-Italic*en-
- Latinin-
- Proto-Indo-European*per-?
- Proto-Indo-European*pres-
- Proto-Italic*pres-
- Latinpremō
- Latinimprimō
- Latinimpressiōnem
- Frenchimpression
- Frenchimpressionner
- Frenchimpressionnable
- Englishimpressionable
- English todayunimpressionable
From un- + impressionable.
Etymology from Wiktionary, CC BY-SA 4.0.