nước lã

Perhaps from nước +‎ lã, with lã deriving from Chinese 冷 (lãnh, “cold”). Compare nước lạnh (“cold water; unboiled water”).

• (Hà Nội) IPA^(key): [nɨək̚˧˦ laː˦ˀ˥]
• (Huế) IPA^(key): [nɨək̚˦˧˥ laː˧˨]
• (Hồ Chí Minh City) IPA^(key): [nɨək̚˦˥ laː˨˩˦]

nước lã

1. unboiled water

   Synonym: nước lạnh

   Đừng uống nước lã kẻo đau bụng.

   Don't drink unboiled water, you'll upset your stomach.

• Strictly speaking, the fact that water is supposed to be boiled is for tea making, but for hygienic purposes, it has always been recommended that people shouldn't drink water straight out of a well or a tap; they should boil it first instead.