张 is a bow 弓 drawn long 长 — stretching the string taut. From stretching came opening and spreading, and from spreading flat things came its job as the measure word for paper, tickets, tables, and faces.
一张纸 a sheet of paper, 一张票 a ticket, 一张桌子 a table. 张 is also one of China's three most common surnames — roughly 90 million people, more than the population of Germany. 紧张 'stretched tight' means nervous; 张开 is to open wide.
A bow 弓 stretched LONG 长 — things OPENED and spread FLAT.
With ~90 million people surnamed 张 and no emperor ever among them, Chinese folklore jokes that the Jade Emperor himself is surnamed Zhang — heaven compensating the throne-less clan.