ehecayo.

Headword: 
ehecayo.
Principal English Translation: 

something vented or filled with air; or, a heavy rain that comes with a whirlwind (see Molina)

Orthographic Variants: 
eecayo
Alonso de Molina: 

eecayo. cosa ventosa o llena de ayre, oaguacero que viene con toruellino de viento.
Alonso de Molina, Vocabulario en lengua castellana y mexicana y mexicana y castellana, 1571, part 2, Nahuatl to Spanish, f. 28r. col. 2. Thanks to Joe Campbell for providing the transcription.

Attestations from sources in English: 

ehecayo (adjective) = full of wind, stormy
Daniel Garrison Brinton, Ancient Nahuatl Poetry: Containing the Nahuatl Text of XXVII Ancient Mexican Poems (1887), 153.

themes: 
Weather, Climate