pistachio
The whole difficulty sits in one pair of letters. Pistachio is easy to hear and easy to say, and then you have to write down a sh sound using c and h, which is the one thing about the word nobody can work out from listening to it. The vowels either side are unstressed and offer no help.
P-I-S-T-A-C-H-I-O · Pistacia vera
English took the Italian spelling pistacchio, dropped one c, and then refused to say the letters the Italian way. In Italian the cch is a hard k. In English the surviving ch says sh, following the pattern of machine and chef. The letters are Italian and the sound is French.
The nut of Pistacia vera, a small tree of Iran, Turkey and central Asia that needs long hot summers and a cold winter to crop. The shell splits along a seam as the kernel swells, which is why a ripe pistachio arrives already half open.