In several previous postings (collected at this link) this blog has considered the poetry form called a sestina: a sestina has 39 lines and its form depends on 6 words -- arrangements of which are the end-words of 6 6-line stanzas; these same words also appear, 2 per line, in the final 3-line stanza.
The American poet Marie Ponsot (1921-2019) invented the tritina, which she described as the square root of the sestina. the tritina is a ten-line poem and, instead of six repeated words, you choose three, which appear at the end of each line in the following sequence: 123, 312, 231; there is a final line, which acts as the envoi -- and includes all three words in the order they appeared in the first stanza. Poinsot has said -- and I agree -- poetic forms like the tritina are "instruments of discovery . . . they pull things out of you." Read more here in an article by poet Timar Yoseloff.)