To truly understand the nature of a particular human concept, it is often useful to first take a look into the etymologies of the words that are used to convey the concept.
Among the most interesting human concepts is the concept of understanding.
The idea that standing in some position enables one to know some object better was, apparently, the inspiration for many words in the Indo-European languages with meaning related to “understanding, getting to know something”. That includes the Old English words forstandan (which eventually evolved into forstå [Danish and Norwegian], förstå [Swedish] , verstehen [German], verstaan [Dutch], etc.) and understandan (that evolved into the English word understand).
It is likely that the prefix for- in forstandan has the meaning “in front of” (i.e. to stand before, to watch, observe, learn, and understand something). But we can’t be exactly sure about that, and the same goes to how the prefix under- should be interpreted in understandan. The prefix in Old English can mean both “under” and “between, among” (i.e. the word can be a metaphor for standing under something and getting to the bottom, or standing in the midst of things and getting to learn about the difference between them).
It is also possible that the word understandan was formed by combining forstandan with undirgi(e)tan (which also means “understand”). To learn more about the etymology of the word understand, you can check out the book An Analytic Dictionary of English Etymology: An Introduction by Anatoly Liberman. There is an entire chapter on it.
On the other hand, the Latin word comprehendere (meaning “to take together, to unite; include; seize” and “to comprehend, perceive”), formed by joining the prefix com- (for “completely”) with prehendere (which means to catch hold of), is the etymon for comprendre [Catalan and French], comprender [Interlingua and Spanish], comprendere [Italian], compreender [Portuguese] and not surprisingly, the English word comprehend. Here, instead of expressing the concept of understanding through a spacial idea (such as in the word understandan or forstandan), the concept was conveyed by the physical idea of taking hold of something, like the more abstract usage of grasp and seize (in “grasping the significance of something” and “seizing the truth”).
Lastly, let’s take a look at the Chinese, Japanese, Korean and Vietnamese languages, which use the characters 理解 (in the case of Korean and Vietnamese, 理解 is the Hanja and Chữ nôm for 이해 and lý giải respectively) to represent the concept of understanding. In Classical Chinese, 理 was initially1 the character for jade carving. It was also used to express the tone and texture of jade, and later it was generalized2, and eventually it was used to describe the principle, the nature, the order, the essence, the logic, the science, and (sometimes) the reason, of something.3 The second character, 解, initially4 meant severing the horns of an ox, and later was generalized to mean “to separate, loosen; to remove (constraint), clear (confusion); to deconstruct.”
1 according to an extract from Shuowen Jiezi, a 2nd-century Chinese dictionary from the Han Dynasty: “理，治玉也。” (where 治玉 means jade carving.)
2 according to an extract from Xunzi, an ancient Chinese collection of philosophical: “形體、色理以目異。” (English translation: The physical forms, colors and textures of things appear differently to different people.)
3 This is a simplified version of the story. To learn more about the origin of the word, consider studying Classical Chinese.
4 according to an extract from Shuowen Jiezi: “解：判也。从刀判牛角。” (where 判 means to cut, 刀 means knife, 牛 means ox, and 角 means horn.)