PIE base of prepositions and preverbs with the basic meanings of ‘forward’, ‘through’, and a wide range of extended senses such as ‘in front of’, ‘before’, ‘early’, ‘first’, ‘chief’, ‘toward’, ‘against’, ‘near’, ‘at’, ‘around’.
Other derivatives include for, far, first, before, beyond, primeval, primitive, perestroika, paramount, perfect, prose, protagonist, proton, and very many others.
[Pokorny *per-2 A ‘to go/pass over; beyond, over’, pp. 810–816.]