The Spanish word 'suspiro' (meaning 'sigh') comes from the Latin word 'suspirium', which also meant 'sigh'. The Latin word was formed by combining two elements: the prefix 'sub-' meaning 'under, below' and the verb 'spirare' meaning 'to breathe'. This combination literally described the act of breathing under or from below, which evolved to specifically refer to the deep breath we take when sighing.

Several common Spanish words share the same Latin root 'spirare' (to breathe): 'respirar' (to breathe), 'espirar' (to expire/breathe out), 'inspirar' (to inspire/breathe in), and 'aspirar' (to aspire/breathe towards). All these words maintain a connection to breath or breathing, though some have developed more metaphorical meanings.

Many English words are related to 'suspiro' through the Latin root 'spirare': 'spirit', 'respire', 'inspire', 'expire', and 'aspire'. The word most directly related is 'suspire', an archaic English word meaning 'to sigh'. While 'suspire' is rarely used in modern English, we can see the same construction of 'sub-' (under) + 'spirare' (breathe) in both Spanish 'suspiro' and English 'suspire'. The breathing-related meaning is also preserved in common words like 'respiration' and 'respiratory'.