The Spanish word 'pera' (meaning 'pear') comes from the Latin word 'pira', which was the plural form of 'pirum' (meaning 'pear'). Interestingly, Spanish adopted the plural form 'pira' rather than the singular 'pirum' as its base, but made it singular again in Spanish. This kind of shift from plural to singular forms occasionally happens in language evolution.

The word 'pera' is fairly basic in Spanish and doesn't have many simpler related words. However, you might encounter 'perita' (little pear) or 'peral' (pear tree) which are derived from 'pera'.

The English word 'pear' is actually a cousin of the Spanish 'pera', as both ultimately derive from the same Indo-European root. While Spanish got its word through Latin 'pirum', English 'pear' came through Germanic languages, but they share the same ancient ancestor. This is why 'pear' and 'pera' sound somewhat similar even today.