Writing or giving a full existing poem as a name for the object based on the impression the object gives . The artist and aristocrat Kobori Enshū 小堀遠州 (1579-1647) is credited for being the first teaist to start naming chashaku with full poems based on his impression from the chashaku. These are called utamei 歌銘 (poem name).

Enshū crafted a chashaku with a single whole in the bamboo. As the summer rains were approaching and the sky at night was becoming more and more clouded, he savoured the last glimpses of the stars at night before the summer rains took over the night sky. Seeing this one tiny hole in the chashaku reminded him of a single star from a break in the cloud. He then composed this poem for the chashaku:

星ひとつ　 Hoshi hitotsu

見つけたる夜 Mitsuketaru yoru

のうれしさは no ureshisa wa

月にもまさる　 Tsuki nimo masaru

五月雨のそら Samidare no sora

In Adam Sōmu Wojciński translation:  

Lo, a single star

A jewel glimpsed through cloudy night

As the moon ages

The summer rains draw nearer

Stars and sky fade to my heart

The leaders of chanoyu (Japanese tea ritual) in its formative years were deft renga poets. The fundamentals of the art of tea were even taught in waka verses. Captured in 31 syllable poems, the core teachings of the art are easier to remember and internalise into the unconscious. Not only for teaching purposes, the tea masters' love of poetry led them to animate the proceedings of a tea gathering with poetical expression, exemplified in their use of hanging poetry scrolls and naming chashaku, tea caddies, tea bowls, fresh water containers and flower vases. Tea masters harvested these exquisite and meaningful mei 銘 from their rich literary tradition and poetry collections. Great literary works such as the Tale of Genji (Genji no Monogatari 源氏の物語) are also rich sources of poetic names. 

Together with waka and haiku, such literary works are studded with kigo 季語 (seasonal words). Kigo are used in waka, haiku and the collaborative linked-verse poetry form of renga, to indicate the season referred to in the stanza. Often two to four syllables, these words carry a strong linguistic register relative to their length. This register is one reason a poetic name for a chashaku rings so profoundly in a tea gathering. The utterance of the mei conjures up idealised visions of seasonal phenomena and nostalgia, romanticising the ambience in the tearoom, enhancing the seasonal or spiritual theme of the gathering. 

As an example from another culture, while reading Braiding Sweetgrass, by Robin Wall Kimmerer, I came across the word puhpowee from the Aboriginal Canadian Anishinaabe people. According to Kimmerer, it means 'the force which causes mushrooms to push up from the earth overnight'. A gem of a poetic name for chashaku if I ever heard one. This is a fitting seasonal word (kigo) for Autumn, the season of mushrooms.

Silent eruption

Black night, white morn', black soil, white-

'shroom puhpowee 

by Sōmu Wojciński

The last example demonstrates something of great importance for chanoyu as a global art form: its associated arts need not be exclusively Japanese. Poetic names for chashaku are but one way disparate cultures can come together through the vessel of chanoyu, deepening our understanding and aesthetic appreciation of foreign arts, languages and cultures.