Is there an English idiom for Bengali idiom "সবজান্তা গামছাওয়ালা"(wise towelsman)?

In the Bengali language there is an idiom, "sobjanta gamchawala" (wise towelsman), meaning a man whose occupation is merely to sell towels, but claims to know everything and gives valuable advice on any and every topic.

As you can imagine, wise and valuable are used here as sarcasm. In Bengali, the phrase is used to point out a person who always makes a comment on every topic without knowing the context.

Is there is an English idiom or phrase for that?

I'm not looking for jack of all trades is a master of none. A jack of all trades is able to do a lot of things fairly well, but sobjanta gamchawala isn't.

Solution 1:

In English, we have the infamous know-it-all: one who knows everything; hence, a person who makes pretension to great knowledge, especially one whose didactic conversational habit conspicuously reveals his belief that he has superior knowledge on many subjects; a wiseacre; a know-all; -- usually ironical. [Colloq. & pejorative] Note: the use of this term implies that the speaker disapproves of this behavior, and may think that it is unjustified.

**know all: someone who seems to know everything and annoys other people by showing how clever they are.

No one likes him because he's such a know-all.

smarty-pants is an older idiom, for one who is obnoxiously self-assertive and arrogant, as is weisenheimer.

There is the Jerkass, who might say something like, "Sometimes I park in handicapped spaces while handicapped people make handicapped faces. I'm an asshole!" (— Denis Leary, Asshole) but this is more trope or jargon.

And, as StoneyB has kindly reminded me, there is the loudmouth:

Be loquacious, often noisily or boastfully; someone who talks too much or too loudly, esp. in an offensive or stupid way

*Harvard Square: Know-it-all capital of the universe. * - Universal Hub.

Solution 2:

I cannot call any fixed phrase to mind, but the role is familiar in American literature. In small towns it is traditionally associated with the barber or hairdresser, and in big cities with the cabdriver—no doubt because in their professions they have captive audiences.

The bartender is a related figure, but tends to be seen rather as a source of genuine wisdom, albeit of a dark and sardonic cast.