pikniko

Decode nothing. This is one of the words where the honest instruction is to stop looking for a seam. Pikniko came out of French pique-nique in one piece, and the pik- you can see at the start has no connection to the Esperanto piki, to prick or sting. Nor is -nik- an ending. Learn it as a single root, the way you learned hotelo, and put the analytical energy somewhere it pays.

The word is a verb too. Piknikumi is the usual way to say to picnic, using the -um- wildcard for a relation the language declines to specify, and you will also see plain pikniki. Both are read without trouble. Piknikejo is the picnic spot, and a piknikkorbo is the hamper.

Register: a small outing, on the grass, with food. It is warmer than ekskurso, which is a day trip and might involve a coach and a timetable, and much smaller than a festo. What travels in the korbo is pano, fromaĝo, frukto, kuko and something to drink, and what the whole thing needs is somero and no pluvo. The verb for the eating is plain manĝi; nobody dresses it up.