There might be a confusion, attested in Procopius (or maybe made just by him) between Greek
píthēkos (monkey) and Latin (Vulgar, reconstructed) forms meaning "small", "little", or derivations of these. Cf. Vulgar Latin, 2000, Herman, Jâozsef, page 101:
the word for “small,” paruus, was replaced everywhere by words that seem really to come from the nursery, such as pitinnus, pisinnus, putillus(teeny)".
Even Wiktionary reflects this: the page for πίθηκος (monkey), beside the figurative meaning "jackanapes/trickster", provides as a third entry the meaning "dwarf". But that seems attested only once, and that occurence may be based on the
confusion with the Vulgar Latin word.
The Greek word seems in fact close to some later local variants:
pittus > pittitus, pittinus, pitticus and
piccus > piccinus, piccoccus, picculus.
These, in turn, have resulted in Romance words like Italian piccino, piccolo, Sardinian piccinu, picciocu, Spanish pequeño, Portuguese pequeno, Albanian picë, "little girl", Romanian pici (small boy), pic (a bit, a drop), French petit (and related), Milanese pitinu, Sardinian pithinnu, piticu, Romanian pitic ("dwarf") and piti, pitit ("to hide", "hidden", like in "make oneself small"). More scholarly references in links below.
As I mentioned in a comment, I don't have knowledge of a direct confusion as you asked for, but reading again those posts initially linked in the comment I have found something that might qualify.
My initial problem was to find the origin of the common Romanian word pitic (dwarf). The etymology in Romanian dictionaries was linking to the Greek πίθηκος - píthēkos (monkey) while many Romance languages and dialects had similar forms that pointed to a Latin origin. There was no "pitikkos" form in Latin, more or less related to the Greek word, and in the end I was convinced of the otherwise obvious Latin origin of the Romanian word, as argued here.
But I was kept for a while hesitating by the fact that Suda lexicon is defining píthēkos also as "what some call a short little man" and linked that meaning to Πίθηξ, "Used in the sense of "dwarf" by Procopius, Gothic War 4.24".
Looking at the sources provided under the Wiktionary page for πίθηκος the meaning is not attested in other sources, and its rarity pleads in favor of a confusion (or maybe a contamination) attested by the 6th century historian Procopius of Caesarea between the Greek word and a late vulgar Latin and early-Romance term meaning "small".
(Procopius' confusion ended up in Suda, was then quoted by various dictionaries, including Wiktionary, and thus became in Romanian dictionaries the basis for a wrong etymology of the word meaning "dwarf".)
Now, trying to identify that word in the text by searching in Procopious works online, I couldn't identify it with the meaning "dwarf". I couldn't find
Πίθηξ in the Gothic Wars, nor the complete works. The only word containing the form
πίθηκες with the meaning "dwarf", and was found in Gothic Wars not at 4.24, but at he very end of 8.24:
ἐνταῦθα, ὥσπερ ἄνθρωποι πίθηκες γίνονται, οὕτω δή τινων ἵππων ἀγέλαι
εἰσὶ τῶν προβατίων ὀλίγῳ μειζόνων.
On that island are found apes just
like men, and there is also a breed of horses only a little larger
(The exact same fragment seems present in Book 8 of The Wars of Justinian)
If the Suda entry is not verified by Procopius, that increases in fact the chances that πίθηκος with the meaning "dwarf" in Greek is due to a contamination from a proto-Romance word.