The Spanish verb 'obligar' (to obligate) comes from the Latin verb 'obligare', which meant 'to bind' or 'to obligate'. The Latin word was formed by combining two elements: the prefix 'ob-' meaning 'against' or 'in exchange for', and the verb 'ligare' meaning 'to bind'. So literally, 'obligare' meant 'to bind against' or 'to bind in exchange for something', which evolved into the modern meaning of creating a binding commitment or obligation.

Several common Spanish words share the Latin root 'ligare' (to bind): 'ligar' means 'to bind' or 'to connect', which is a simpler and more literal preservation of the original Latin meaning. 'Liga' means 'league' or 'band', representing a group bound together. These words help show how the concept of binding or connecting underlies the more abstract notion of obligation in 'obligar'.

Many English words are related to 'obligar' through the same Latin roots. Most obviously, 'obligate' and 'obligation' come from the same Latin 'obligare'. The English word 'ligament' (tissue binding bones together) comes from Latin 'ligare'. We can also see this root in words like 'league' (a binding together of people or teams), 'liable' (bound by law), and 'ally' (bound in partnership). The prefix 'ob-' appears in English words like 'obstacle' (something standing against) and 'obvious' (placed in front of).