What are your thoughts on the term ‘empty barrel’ to describe a person? What does it mean and what’s the origin?

'An empty barrel makes the most noise' may be a more modern derivation of older sayings about 'empty vessels'.

The 1908 book, A Dictionary of Thoughts by Tryon Edwards, features not one but two 'empty vessels' quotes, one from Plato and the other from Shakespeare. Book itself is available for free download here: https://ia800302.us.archive.org/...

A Dictionary Of Thoughts, page 560, Plato.

As empty vessels make the loudest sound, so they that have least wit are the greatest babblers.

A Dictionary Of Thoughts, page 46, Shakespeare.

The empty vessel makes the greatest sound.

Comments in a discussion thread from Did Plato say this? (see below, quotes in italics) offer several examples of 'empty vessels' usage in English over the centuries. Gist is 'all talk, no action' or 'ones who act, don't talk, those who talk, don't act'.

"I have always observed that your empty vessels sound loudest"
Jonathan Swift in "A tritical essay upon the faculties of the mind"
Published in "The Works" in 1803 by J. Johnson. (See page 270).

15 years later comes this:
"Empty vessels make the greatest sound.
The Scripture saith, A fool's voice is known by multitude of words. None more apt to boast than those who have least real worth ; least whereof justly to boast. The deepest streams flow with least noise."
 Page 71 of "A compleat collection of English proverbs of the Scotch, Italian, French, Spanish and other languages" by John Ray, published in 1818

Consider the following passage:
" Empty vessels make always the loudest sound; the less virtue, the greater report. Deep rivers pass away in silence ; profound knowledge says little ; but what a murmur and bubbling, yea, sometimes what a roaring, do they make in the shallows ! The full vessel gives you a soft answer, but sound liquor. Samson slew a lion, but he made no words of it: the greatest talkers are the least doers. As when a rabbi, little learned, and less modest, usurped all the discourse at table; one much admiring him, asked his friend in private, whether he did not take such a man for a great scholar: to whom he plainly answered, Fог aught I know he may be learned, but I never heard learning make such a noise. Religion is much heard of in our words, but it is little seen in our works. We have busy tongues, but lazy hands; and this argues but vain hearts ; we may be still empty vessels. By their unseasonable noise, men are known for empty vessels."
 Page 843 of "An Exposition Upon the Second Epistle General of St. Peter" by Thomas Adams and James Sherman, published by Henry G. Bohn in 1848.

In Shakespeare's Henry V, the character called "Boy" ends a scene with an aside about Pistol (a pompous and bombastic character) which begins as follows:
"I did never know so full a voice issue from so empty a heart: but the saying is true 'The empty vessel makes the greatest sound.' "
Shakespeare Henry V, Act IV, scene 4, line 72 (c. 1599)

pre-1430
 John Lydgate 
Pilgrimage of Man l. 15933
 A voyde vessel‥maketh outward a gret soun, Mor than‥what yt was ful.

1547
 William Baldwin
 Treatise of Moral Philosophy iv. Q4
 As emptye vesselles make the lowdest sounde: so they that haue least wyt, are the greatest babblers.

1599
 [Shakespeare, Henry V, already quoted above]

1707 
Swift Essay on Faculties of Mind I. 249 
"Empty Vessels sound loudest." [more fully quoted above]

https://www.quora.com/What-are-your-thoughts-on-the-term-%E2%80%98empty-barrel%E2%80%99-to-describe-a-person-What-does-it-mean-and-what%E2%80%99s-the-origin/answer/Tirumalai-Kamala