The Spanish word 'largo' meaning 'long' comes from the Latin word 'largus', which meant 'abundant' or 'copious'. The semantic shift from the Latin meaning of 'abundant/copious' to the Spanish meaning of 'long' likely occurred because something that is long can be thought of as extending abundantly in space. This kind of meaning change, where a word shifts from a general concept of abundance to a more specific spatial dimension, is fairly common in language evolution.

A related Spanish word is 'largueza', meaning 'generosity' or 'liberality', which retained a meaning closer to the original Latin sense of abundance. Another related word is 'alargar', meaning 'to lengthen' or 'to extend', which combines 'largo' with the prefix 'a-' to create a verb.

While English 'large' might look similar to Spanish 'largo', they actually have different origins - 'large' comes from Latin 'largus' but developed the meaning of 'big' or 'great' in size rather than 'long'. The English word 'largesse' (meaning generosity) is also related, and like Spanish 'largueza', it preserved more of the original Latin meaning of abundance.