The Spanish word 'decano' (meaning 'dean') comes from the Latin word 'decanus', which meant 'leader of ten men'. This Latin term was itself derived from 'decem', the Latin word for 'ten'. Originally, a 'decanus' was a military term referring to an officer who commanded a group of ten soldiers. Over time, the term evolved to refer to leaders or senior members in various organizational contexts, particularly in academic and ecclesiastical settings, giving us the modern Spanish 'decano'.

Some related Spanish words that share the Latin root 'decem' (ten) include: 'década' (decade), 'decimal' (decimal), and 'diciembre' (December, originally the tenth month in the Roman calendar). These words all preserve the connection to the concept of 'ten' in their meanings.

English speakers might recognize the connection to words like 'dean' (which is a direct cognate of 'decano'), 'decade', 'decimal', and 'December'. All these words share the same Latin ancestry related to 'decem' (ten). The English 'dean' underwent the same semantic evolution as Spanish 'decano', moving from a military leader of ten to an academic or ecclesiastical leader.