The Spanish verb 'pulular' (meaning 'to swarm' or 'to multiply') comes from the Latin verb 'pullulare', which meant 'to sprout' or 'to multiply'. This Latin verb was derived from 'pullus', which referred to a young animal, particularly a chick, or a sprout. The semantic evolution from referring to young animals and sprouts to the modern meaning of swarming or multiplying is quite natural, as both concepts involve growth and increase in numbers.

While 'pulular' might seem isolated in modern Spanish, it's worth noting that the Latin root 'pullus' (meaning young animal or chick) also gave rise to the Spanish word 'pollo' (chicken), though this connection might not be immediately apparent due to the different vowel sounds.

English speakers might recognize a connection to words like 'pullet' (a young hen), which also comes from the Latin 'pullus'. The word 'poultry' is another English relative, ultimately derived from the same Latin root, showing how the original meaning of 'young bird' or 'chick' has been preserved in these English terms while the Spanish 'pulular' developed along a different semantic path to mean 'to swarm' or 'multiply'.