Intelligible is of multiple origins. Either (i) a borrowing from French. Or (ii) a borrowing from Latin. Etymons: French intelligible; Latin intelligibilis, intellegibilis "that can understand; that can be understood,"  In Middle English also "to be grasped by the intellect" (rather than the senses). In English, sense of "capable of being understood, that can be understood" first recorded c. 1600. Related: Intelligibly. 

The first known use of the word "intelligible" in English was in the 14th century, specifically in the Middle English period. It was borrowed from Latin, with the Latin word "intelligibilis" as its origin. The Oxford English Dictionary's earliest evidence for "intelligible" is from before 1382, in the Wycliffite Bible (early version).  

Examples of using Intelligible in a sentence: 
"How much can you leave out while keeping it intelligible, he asks?" "
"What we need a program that can display this data in an intelligible form" 
"While it's clear and intelligible, a musical really deserves at least a stereo soundtrack." 
"By doing this, it would make the system more intelligible to the general public" 
"Why is the entire issue of footballers' pay invariably lost in a maelstrom of barely intelligible envy?" 
"He makes silly films intelligible." 
"The hurricane of 1938 followed a path that is perfectly intelligible, in retrospect."

Just the facts:

INTELLIGIBLE Definition & Meaning - Merriam-Webster