In Medieval and Edo Japan, poets often wrote collaborative poems called renga. One special guest author during a meeting of renga would provide a hokku, a 5-7-5 sound (or syllables in the west) verse, similar to what we now call a haiku. The other poets at a renga meet would try to provide the best waki, a two-line response of 7-7 sounds (in the west syllables).
In our modern age, the 5-7-5 hokku when written under certain precise circumstances becomes what we call a haiku…when we add two more 7-7 lines we have a tanka…unless like today, we add our waki to a haiku written by someone else, then we have a renga!
Chèvrefeuille provided today’s hokku (haiku) himself:
in the backyard
the rainbow in the bird bath breaks –
a sipping Magpie
impertinent young robin
dove into the wet colors