“Testament; From the word Testes, referring to the male generative organs, where the ‘seeds of life,’ are kept. Words were often thought of as the seeds of life. Moreover, the word Testes also connotes the light of the sun, without which all writing and reading would be impossible.
The reason why one writes from left to right was because this is how the sun moved, from east to west across the sky.”

Source: Astro-Theology Etymology and Sidereal Mythology Tarot Astronomy