What’s in a name? That which we call a rose,
By any other word would smell as sweet.
Izayoi (十六夜) translates to “sixteenth night”, an abbreviation of Izayoizuki (十六夜月) meaning “sixteenth night moon”. The full moon occurs on the 15th night of the lunar month, hence the 16th night marks the start of the moon’s waning. The moonrise on the 16th night happens around 7pm at dusk falls, seemingly hiding until sunset before coming out. This act of hesitation by the moon has given 十六夜 its modern pronunciation of izayoi, derived from 猶予う (izayou) meaning to hesitate.
『十六夜は わづかに闇の 初哉』
Sixteenth night moon— / ever so slightly / the darkening begins
(translated by David Landis Barnhill)
Matsuo Basho, famous poet of the Edo period in Japan, wrote this haiku poem on the 16th night of the 8th lunar month in Genroku year 6 (1693). He described the waning moon on the 16th night as the start of its darkening. This symbolism is reflected in Izayoi Aki through her descent into darkness becoming the Black Rose Witch. Her birthday on 16 August is perhaps also derived from 16th night of the 8th month.
The full moon is the brightest on the 8th lunar month, and this autumn moon is honored with a moon-viewing festival Tsukimi. Autumn is Aki (秋) in Japanese, though Izayoi Aki name is spelled as 十六夜アキ and so the exact meaning of her Aki (アキ) cannot be affirmed.
Chestnut Rose (Rosa roxburghii) is also known as Izayoi Bara (十六夜薔薇) meaning “sixteenth night rose”. The name Izayoi Bara originates from the flower often having missing petals, making it incomplete like the sixteenth night moon. The Izayoi Bara blooms from Spring to Autumn.