The Spanish word 'ají' comes from the Taíno word 'aší', meaning 'chili pepper'. Taíno was the principal language of the indigenous peoples of the Caribbean when Spanish colonizers arrived in the Americas. This is one of many words that Spanish borrowed from Taíno languages during the early colonial period, particularly for flora and fauna native to the Americas that were previously unknown to Europeans.

Since 'ají' entered Spanish directly from Taíno, there aren't any simpler or more common Spanish words that share its etymology. However, it's worth noting that while 'ají' is the common word for chili pepper in many parts of Latin America, particularly the Caribbean, other Spanish-speaking regions might more commonly use 'chile' (from Nahuatl) or 'pimiento' (from Latin).

There aren't any etymologically related English words since 'ají' comes from Taíno. However, English speakers might recognize this word from Latin American cuisine, where it appears in dish names and sauce names, particularly in Caribbean cooking. The English word 'chili' comes from a different indigenous American language (Nahuatl) and is not etymologically related to 'ají'.