grow late, night watch, sit up late, of course, renew, renovate, again, more and more, further
更 centers on the idea of change or progression: renewing, renovating, or moving further. The senses of growing late, night watch, and sitting up late are natural extensions of time advancing, while 'of course' reflects a logical next step.
更 originally depicted a hand holding a whip or tool, suggesting correction or change. Over time, the meaning broadened to renewal and progression. The modern form is simplified, and the exact historical development of its components is uncertain.
The top horizontal line and the box-like 日 below with a vertical stroke through it look like a tool being used to reshape something. Think of 更 as a tool for renewal: it changes things, makes them further, and pushes time later.
For コウ, imagine a clock that keeps ticking later and later, making a 'ko' sound each time it advances: ko -> コウ, and the night watch sits up late as time renews.
furthermore; again; after all; more and more; moreover; even more
change; modification; alteration; revision; amendment
renewal; update; replacement; renovation; breaking (a record)
now (when it is already much too late); at this stage
one-fifth of the night (approx. 2 hours)
even more; still more; further
still more; even more; all the more
rehabilitation; remaking one's life; starting life anew
to sit up late
changing one's clothes
change (of personnel); reshuffle (e.g. of a cabinet); shake-up; dismissal (e.g. of a minister); replacement
menopause; climacteric
empty lot; vacant plot of land
correction; revision; rectification
(not) altogether; (not) wholly
intentionally; deliberately; designedly; on purpose
staying up late; sitting up late at night; keeping late hours
to get late; to advance; to wear on
late at night; small hours of the morning
chintz; calico; printed cotton