That is called Fiddleback Maple (Maple with very tight curl like that has been prized for violin fronts & backs for centuries),Tiger Maple,Curly Maple among other names.Both Hard & Soft Maples are known to have it,though Hard Maple is more common. The grain pattern also appears in Red & White Oak,Black Cherry & Black Walnut on occasion.Prized for veneer,not often found in large pieces,normally scattered throughout the main trunk or random branches.Especially when the tree is under some form of stress,growing irregularly.Can appear when the branch or trunk has a slight bend,or near a knot,but not always.
Here's a piece of Bur Oak I found years ago.Managed to cut a few small pieces that didnt crack & split during drying.Was a medium sized tree about 40 ft tall growing at edge of farm field,part of lower trunk had barb wire fencing embedded in a couple places.Very hard & even harder to split with maul due to the heavy cross grain.Beautiful stuff when smoothed & polished though.The varnish has yellowed a bit over the years,but its not too far from 'normal' color for this stuff.Ironwood(Hophornbeam) mallet next to it,with similar grain pattern.
Next 3 pic are Hard Maple & Walnut router bit box I made in 1995.Gives a good idea what you can do with this stuff :coolsmile: