Leading I - description applies per-instance.
Leading C - description applies across all instances of the class
OTO - One Thread Only. The thread that owns the object is the only one that may use it.
OTT - One Thread At A Time. Any thread may use the object, but only one at a time. Use some kind of mutual exclusion mechanism to allow multiple threads to safely access the same object.
GRP - Group. It's complex, in that different groups of members have different access rules, and context dictates whether some particular useage is allowed when other threads are already using the object.
R/W - Reader/Writer. A special (and common) case of GRP. One writer may access the object, or multiple readers may access the object.
FT - Free Threaded. Anything goes.