'Portable' is the most transparent '-port' word — Latin 'portare' (to carry) + '-bilis' (able). Carry-able.
Able to be easily carried or moved, especially because of being a lighter or smaller version than usual.
From Late Latin portābilis (that can be carried), from Latin portāre (to carry, to bear a burden), from PIE *per- (to lead, to pass over, to carry through). The PIE root *per- is one of the most pervasive in Indo-European, appearing in English fare (to travel, from Germanic *farjaną), ford (a crossing place), ferry (a boat that carries across), and further. Latin portāre gives the entire port- family: port (a harbour, where goods are carried in), portal, portfolio (a carrying case for leaves
A 'porter' (someone who carries luggage), a 'portfolio' (a carrying case for papers, from Italian 'portafoglio' — carry-leaf), and a 'portmanteau' (a large traveling bag, from French 'portemanteau' — carry-cloak) are all direct relatives of 'portable.' The word 'porter' also gave its name to porter beer — a dark ale popular with London street porters in the eighteenth century.