The only free and comprehensive online etymological dictionary of the Spanish language
latir (Verb) (of the heart) "to beat;" (of dogs) "to yelp"
Very early 14th cent. From Latin glattire "to yelp." Latin intial gl- could reduce either l- or ll- or both (Cf. Latin glans "acorn" to llande and lande). Of unknown origin.
Portuguese latir, French glapir