Principal English Translation: 

deity of the night (see Sahagún)

Orthographic Variants: 
Attestations from sources in English: 

in oommoten ixqujch iauqujzquj, in ie inman in ooalhuetz acaujztli, in tlaioalli injc tlaiooalcujoaz = All the warriors were extended there, until the moment that Yacauitztli, [god of] the night, would descend–that darkness would fall (central Mexico, sixteenth century)
Fr. Bernardino de Sahagún, Florentine Codex: General History of the Things of New Spain; Book 8 -- Kings and Lords, no. 14, Part IX, eds. and transl. Arthur J. O. Anderson and Charles E. Dibble (Santa Fe and Salt Lake City: School of American Research and the University of Utah, 1951), 52.