Like many of the Mother Goose rhymes, the verse about the Tommyknockers is deceptively simple. The origin of the word is difficult to trace. Webster’s Unabridged says Tommyknockers are either (a) tunneling ogres or (b) ghosts which haunt deserted mines or caves. Because “tommy” is an archaic British slang term referring to army rations (leading to the term “tommies” as a word used to identify British conscripts, as in Kipling—“it’s Tommy this, an’ Tommy that …”), the Oxford Unabridged Dictionary, while not identifying the term itself, at least suggests that Tommyknockers are the ghosts of miners who died of starvation, but still go knocking for food and rescue.
Stephen King, The Tommyknockers, 1987
In a deceptive or deceiving manner; so as to deceive.
Usage Note: When deceptively is used to modify an adjective, the meaning is often unclear. Does the sentence The pool is deceptively shallow mean that the pool is shallower or deeper than it appears? When the Usage Panel was asked to decide, 50 percent thought the pool shallower than it appears, 32 percent thought it deeper than it appears, and 18 percent said it was impossible to judge. Thus a warning notice worded in such a way would be misinterpreted by many of the people who read it, and others would be uncertain as to which sense was intended. Where the context does not make the meaning of deceptively clear, the sentence should be rewritten, as in The pool is shallower than it looks or The pool is shallow, despite its appearance. [AHD4]
used for saying that something is different from how it appears:
The house looks deceptively small from the outside (=but really it is big). [MEDA]