PIE base base ‘to change, go, move’, with derivatives referring to the exchange of goods and services within a society as regulated by custom or law.
Derivatives, other than those listed below, include in English common, mutate, mutual, miss ‘in a changed manner’, municipal ‘service performed for the community’, and migrate; in Sanskrit maitreya ‘friendly, benevolent’, from maitrī ‘friendship, benevolence, good will’, from mitra ‘friend, companion, associate’; and in Pāli mettā ‘loving-kindness’, the translation of Sanskrit maitrī, akin to Buddhist compassion (karunā) and love or charity (agapē) in Christianity.
[Pokorny *mei-2 ‘to change, exchange’, *mei-3 ‘to wander, go’, p. 710, *mei-gu̯- ‘to (ex)change’, p. 713, *mei-t(h)-2, ‘to (ex)change’, p. 715.]