Profusely means in such abundance that it pours out unchecked. Sweat, blood, thanks or apologies.
It attaches to a small and oddly specific set of verbs, since bleeding profusely, sweating profusely, apologising profusely and thanking somebody profusely account for nearly every use of the word. The first two are physical and the last two are social, and all four involve more than would be expected. The adjective profuse is far rarer, and profusion means an abundance.
1adverbprofuselyIn large amounts, flowing or given freely.
“He apologised profusely and offered to pay.”
Proto-Indo-European
*per-
Latin
profusus
English
profuse
English, today
profusely
From profuse + -ly. profuse comes from Latin profusus.
Etymology from Wiktionary, CC BY-SA