The Spanish word 'guayacán' comes directly from the Taíno word 'waiacan', which referred to the guaiacum tree. This is one of many words that Spanish borrowed from the indigenous Taíno people of the Caribbean when the Spanish first arrived in the Americas. The Taíno were the primary inhabitants of Cuba, Hispaniola, Puerto Rico and other Caribbean islands. The word maintained both its form and meaning quite closely as it was adopted into Spanish, with only minor spelling adaptations to fit Spanish phonology.

Since 'guayacán' comes from Taíno rather than Latin or Greek roots, there aren't many etymologically related simpler Spanish words. However, you might encounter variations like 'guayaco', which refers to the same tree or its resin, used in traditional medicine.

In English, this tree is known as 'guaiacum', which is also borrowed from the same Taíno source word, though it entered English through Spanish and Latin scientific nomenclature. The English term 'lignum vitae' (meaning 'wood of life') is also used for this tree, though this is a Latin-derived name rather than being etymologically related to 'guayacán'.