券
けん · ken · JLPT N3 · noun
ticket
🎫 券 = 龹 + 刀 knife: old contracts were wooden tallies cut in two
In ancient China, a deal was carved on a wooden tally and split with a knife (刀). Each party kept one half as proof, which is how 券 came to mean ticket or certificate. It appears in 乗車券 (jōshaken, train ticket).
券 — ⺉ knife radical + 龹 (phonetic top)
Originally written 券, depicting a tally cut with a knife (刀/⺉) into two halves so each party could keep proof of an agreement. The top element 龹 supplies the sound. From this 'split tally' sense it came to mean a certificate, ticket, or voucher.