How does '一勿' Compound to mean sundial? Etymology [of 腸]
Ideogrammic compound (會意): 日 ‎(“sun”) + 一 + 勿   The rays of the sun.
[ From chineseetymology.org: ]
Primitive pictograph 昜. From sun日 (rays) on a sun dial (一勿). Meaning bright.

My research of the etymology of 腸 motivated this question. I know that 一 means one, and that 勿 means 'not' or 'do not' (ie: negation).
勿 as in "not" is originally a logograph of a signaling flag. It is not the same logograph as the rays depicted in 昜 (which is 日 rì over  yáng).

It is not uncommon for Chinese characters to have merged similar logographs into one single abstract unit, in the latter case 旦 over 勿.

Take for example 易 (yì), which is unrelated to 昜, although its modern components are 日 and 勿. It is derived from the logograph of a chameleon.