垃垃

First syllable from a lenited form of 在 (MC dzojX|dzojH) (Qian, 1997) which later experienced glottalization and potential assimilation with 拉, mainly in circa 19th century Shanghai (Qian, 2003).

The second syllable is likely cognate with the personal pronoun pluralizer in e.g. Shanghainese 拉, which may in itself be a lenited non-checked tone variant of 搭 according to (Qian, 2003) and (Sheng, 2013). Compare 在𡍲.

Alternatively this might be a reduplicated form of 垃.

The aspect marker senses are part of a commonplace semantic derivation in Wu and some of Gan, whereby preposition-demonstrative phrases come to be grammaticalized as stative verb markers (Qian, 1997).

垃垃

1. (Northern Wu, including Shanghainese) to be at; to be in

垃垃

1. (Northern Wu, including Shanghainese) at; in
   • 2023, 饭瓜子, “强风大背头”‎^[1]performed by 摇铃鸟, cover of 強風オールバック:

     一家頭拉拉屋裏蹲垃，人出蘑菇快哉要。 [Northern Wu, trad.]
     一家头拉拉屋里蹲垃，人出蘑菇快哉要。 [Northern Wu, simp.]

     ⁷iq-ka₁-deu₂ ⁸laq-la₁ ⁷oq-li ¹tin-la₀ ²gnin ⁷tsheq ²mo-ku₁ ³khua ⁰taeq ³iau [Wugniu]

     Been staying at home, feel like mushrooms are gonna grow on me.

垃垃

1. (Northern Wu) be ...-ing; in the middle of doing something (indicating an action in progress)
2. (Northern Wu) Used to indicate the perfective aspect.