The Hebrew noun ayin (עַיִן) means eye, but also spring or fountain of water. It appears over 880 times, making it one of the most frequent nouns in the Hebrew Bible. As the letter Ayin (ע), it represents seeing and perception.
The ayin is the primary metaphor for wisdom and discernment. "The eyes of the LORD" range throughout the earth (2 Chronicles 16:9). To have "good eyes" is to be generous (Proverbs 22:9). The ayin as spring points to life-giving water — the wells of salvation (Isaiah 12:3). Both senses converge in John 4: Jesus meets a woman at a well and offers eternal life.