Probably from Tägäräk *bulɑːn "elk."
Mulan earliest appearence is in the poem below during the Tabğaç Wei dynasty.
木蘭詩二首(古辭)
Two Poems on Mulan (in ancient dictation)
《古今樂錄》曰:「木蘭不知名,浙江西道觀察使兼御史中丞韋元甫續附入。」
The Musical Records of Past and Present states: "Mulan's name is not well-known. Wei Yuanfu, the Western Dao Temple's Inspector at Zhejiang and concurrent Imperial Censor-in-Chief, added it later."
唧唧復唧唧,木蘭當戶織。不聞機杼聲,唯聞女歎息。
Çit çit and again çit çit, Mulan weaves facing the door. The sound of the loom is not heard, only the sighs of the girl.
問女何所思,問女何所憶,女亦無所思,女亦無所憶。
They ask the girl what she is pondering, what she is remembering. She is pondering nothing... remembering nothing...
昨夜見軍帖,可汗大點兵。軍書十二卷,卷卷有爺名。
Last night, she saw the army notice, that the Qağan was calling a great draft. A dozen rolls of military scripts, each one with her father's name (on it).
阿爺無大兒,木蘭無長兄。願為市鞍馬,從此替爺征。
The father has no elder son and Mulan has no older brother. (She) wishes to buy a saddled horse and from then on, march on her father's behalf.
東市買駿馬,西市買鞍韉,南市買轡頭,北市買長鞭。
(She) bought a fine steed from the Eastern Market, a saddle with a saddle cloth from the Western Market, a bridle from the Southern Market, and a long whip from the Northern Market.
旦辭爺娘去,暮宿黃河邊。不聞爺娘喚女聲,但聞黃河流水鳴濺濺。
At dawn, she left her parents and at dusk, she camped at the edge of the Yellow river. (She) could not hear the sounds of her parent's calls. (She heard) only the flowing waters of the Yellow river cry zin zin.
萬里赴戎機,關山度若飛。朔氣傳金柝,寒光照鐵衣,將軍百戰死,壯士十年歸。
Ten thousand li she journeyed to war, mountains and passes she crossed as if in flight. The Northern Winds carried the sounds of the watchman's clappers (as) the cold light shines on her coat of iron. The army general dies after a hundred battles (as) the great soldier returns after ten years.
歸來見天子,天子坐明堂。策勳十二轉,賞賜百千強。
Upon returning, (she) met the Son of Heaven, who sat within the Hall of Brilliance. (Her) merits and achievements are recited a dozen times and rewards conferred hundreds and thousands (of times).
可汗問所欲,「木蘭不用尚書郎,願馳千里足,送兒還故鄉」。
The Qağan asks what she desires. "Mulan does not require a position within the court. (She) desires (only) a fine steed to carry (her) back to her home."
爺娘聞女來,出郭相扶將。阿姊聞妹來,當戶理紅妝。
(When) the parents heard their daughter was coming, they go out the outer city walls, leaning on one another. (When her) elder sister hears that her younger sister is coming, she adjusts her rouge facing the door.
小弟聞姊來,磨刀霍霍向豬羊。開我東閣門,坐我西間床。
(When her) younger brother heard that his younger sister was coming, he sharpened his knife at the grindstone facing swine and sheep. I open the door to my eastern chamber and sit on my bed in the western chamber.
脫我戰時袍,著我舊時裳。當窗理雲鬢,挂鏡帖花黃。
I take off my war-time robe and wear my former clothing. Facing the window, I adjust my hair fringes. Hanging a mirror, I apply yellow powder.
出門看夥伴,夥伴皆驚惶。「同行十二年,不知木蘭是女郎」。
I left out the door to see my companions (who) were all surprised. "We traveled together for a dozen years and never knew Mulan was a young girl!"
雄兔腳撲朔,雌兔眼迷離。雙兔傍地走,安能辨我是雄雌。
The buck bounds here and there, whilst the doe has narrow eyes. But when the two rabbits run side by side, how can you tell the female from the male?