old
古 centers on the idea of something being old, from a past time, or having aged.
古 combines 十 (ten) and 口 (mouth), traditionally explained as many mouths passing down stories from ten generations ago, symbolizing oldness.
Ten 十 mouths 口 telling the same old story over and over: that's how things become old.
For コ, imagine an old, dusty coat hanging in a closet: coat -> コ, and the coat is so old it's falling apart.
ancient city; former capital
old; aged; ancient; antiquated; antique; timeworn
Nagoya (city)
used; second-hand; old
ancient times; distant past; antiquity
classic (work, esp. book); the classics
practice; practising; training; study
ancient burial mound; barrow; tumulus
from ancient times; from old times; from time immemorial
the oldest; the earliest
senior; veteran; old-timer
old clothes; secondhand clothing
ancient times; prehistoric times
ancient and modern times; all ages; past and present
archaeology; archeology
secondhand book
old book; rare book; classic
old haunts; former homes
secondhand bookshop; secondhand bookstore; secondhand bookseller
antiquity; ancient times; bygone days; former times
stale; old fashioned; hackneyed; trite; antiquated; obsolete; musty; outdated
old-fashioned; archaic; antique; antiquated
ancient writing (Edo-period or older); classical literature
old castle; old fortress