Engo (verbal association) is a rhetorical technique in waka poetry, where two or more semantically associated words are used in a poem to express one's sentiments.
Engo are often coupled with kakekotoba (pivot words).
In the following examples, engo are marked by quotation marks.
A waka by Koshikibu no Naishi:
Oeyama ikunonomichi no tookereba mada "fumi" mo mizu ama no "hashidate" (Mt. Oe and the road that goes to Ikuno are far away, so I have neither seen a "letter" from, nor "travelled by foot" there to Amano "hashidate" [In this poem, "fumi" means both a "letter" and to "travel by foot," and although Amano-Hashidate is a place, the "hashidate" is also a reference to the "ladder" to heaven])
A waka by Imperial Princess Shikishi:
Tamano "o" yo "tae" nabataene "nagaraheba" shinoburukoto no "yowari" mozosuru (Let the "cord" of my life be "snapped" if it has to be; Were it "prolonged," it would "fray" as I would not be able to hide this love any longer [In this poem, the "o" refers to both a "cord" and "life," "tae" means to "die out"])