更深

deep at night

to change or replace / to experience / one of the five two-hour periods into which the night was formerly divided / watch (e.g. of a sentry or guard)

more / even more / further / still / still more

old variant of 深[shen1]

deep / depth / deeply / (of a color) dark / deep / rich

deep (lit. and fig.)

deep at night and all is quiet (idiom)