Accommodation is all about making room — it can mean a room or place where you will stay or an agreement about sharing something.
If the only accommodation at Grandma's is the bunk bed and you and your sis decide to take turns on the top, you've made an accommodation regarding your accommodations. When you are accommodating someone, you are making room for them or special circumstances for them. For example, the student with the broken hand was granted the accommodation of having a scribe write his answers for the test. Always remember that accommodation is an accommodating word — there's room inside for two m's and two c's.