`Beware the Jabberwock, my son!
The jaws that bite, the claws that catch!
Beware the Jubjub bird, and shun
The frumious Bandersnatch!'
--Jabberwocky by Lewis Carroll.
Frumious, like so many other words, was coined by Lewis Carroll in his book Through the Looking-Glass and What Alice Found There (1872). It is a Portmanteau word, combining 'fuming' and 'furious' into one writhing unit.
"Take the two words 'fuming' and 'furious'. Make up your mind that you will say both words, but leave it unsettled which you will say first. Now open your mouth and speak. If your thoughts incline ever so little towards 'fuming', you will say 'fuming-furious'; if they turn, by even a hair's breadth, towards 'furious', you will say 'furious-fuming'; but if you have that rarest of gifts, a perfectly balanced mind, you will say 'frumious'."
--Preface to The Hunting Of The Snark
While it was its use in Jabberwocky that made frumious famous, Carroll also used it in The Hunting Of The Snark, again to refer to the Bandersnatch.
He offered large discount--he offered a check
(Drawn "to bearer") for seven-pounds-ten:
But the Bandersnatch merely extended its neck
And grabbed at the Banker again.
Without rest or pause--while those frumious jaws
Went savagely snapping around-
He skipped and he hopped, and he floundered and flopped,
Till fainting he fell to the ground.
--The Hunting of The Snark, The Banker's Fate.
Unlike chortle and galumph, frumious has not entered general usage (yet), although on those rare occasions where one refers to a Bandersnatch, it is usual to refer to it as a frumious Bandersnatch (as if there were any other kind!) Indeed there are both a satirical newspaper and a psychedelic rock band named Frumious Bandersnatch.