Da Ya Liang
大压梁 (dà yā liáng), a chinese go term, for this shape.
Two possible White continuations are the extension at a and the atari at b. b leads to many complications. Only one possible continuation after b is shown below.
White extends
Now White has two choices: the atari of a or the atari of b
Tapir: Isn't a typical case of 1-2-3 principle. If one connects at
anyway, should one not play there first leaving more possibilities after Black defends at
? Most notably the cut at a?