Frankly means speaking openly, even if it is unwelcome. Frankly, it won't work, speak frankly, quite frankly.
At the start of a sentence it warns that what follows is blunt, and it usually softens the offence by admitting it in advance. Quite frankly is a filler and adds nothing. Note that the frank in it comes from the Franks, who alone were free in conquered Gaul.
1adverbfranklySpeaking openly, even if it is unwelcome.
“Frankly, I think your plan is a waste of money.”
frankly is a manner of speaking.
Proto-West Germanic
*frankō — javelin, spear
Old French
franc — free
Middle English
frank
English
frank
English, today
frankly
From frank + -ly. frank comes from Middle English frank, from Old French franc (“free”), in turn from the name of an early gem - confederation, the Frank, from Proto-West Germanic frankō (“javelin, spear”). a doublet of Frank and franc and farang.
Etymology from Wiktionary, CC BY-SA