一六

いちろくichiroku

noun

1. (rolling) a 1 and a 6 (with two dice)
2. dice gambling
3. (armed) robbery
4. mugging
5. Edo period to early Meiji non-working day falling on all days of the month with a 1 or a 6 in it (when written in kanji numerals, i.e. the 1st, 11th, 16th, 21st and 26th days of the month)

Study it in Yanamino