learning, knowledge, school
學 centers on acquiring learning and knowledge, especially in a structured setting like a school.
學 is the traditional form of 学. It originally depicted two hands (臼) passing down knowledge under a roof (冖) to a child (子), symbolizing teaching and learning.
The top 臼 looks like two hands exchanging a book, under a cover 冖, with a child 子 at the bottom receiving knowledge. Together, 學 shows learning being passed down in a school.
For ガク, imagine a student at school exclaiming 'Gak!' when they finally understand a difficult lesson: 'Gak!' -> ガク, the sound of sudden learning.