terrathree

Translingual

From 1959 ITU proposals ter and tree, the former perhaps from Italian terzo and the latter from NATO/ICAO three (pronounced "tree").

terrathree

(rare) (international standards) ITU & IMO radiotelephony clear code (spelling-alphabet name) for the digit 3.
Synonym: three (NATO/ICAO)

ICAO/NATO vs ITU/IMO radiotelephonic clear codes for digits
ICAO/NATO	zero	one	two	three (tree)	four (fower)	five (fife)	six	seven	eight	nine (niner)
ITU/IMO	nadazero	unaone	bissotwo	terrathree	kartefour	pantafive	soxisix	setteseven	oktoeight	novenine

^ That is, with each syllable stressed and the last syllable like tree, as in NATO/ICAO three. International Maritime Organisation (2005). International Code of Signals, p. 22–23. Fourth edition, London.