impressively comes from impressive (from Latin impressus, past participle of imprimere 'to press into', from in- 'into' + premere 'to press') + the adverbial suffix -ly. Morphologically, the ending is part of the etymology: the suffix is attached to the older base named in the history, producing a later English derivative. In present English, the adverb sense is "in a way that arouses admiration through scale, skill, or quality", so the historical development ends in a clearly identifiable modern dictionary use. The same base also appears in related forms such as impressive, impress, and impression. Its semantic neighborhood includes strikingly, remarkably, notably, and grandly, which helps locate the modern sense without adding a separate etymological claim. The named historical forms include Latin imprimere and Latin premere.