はしご高

梯子 (hashigo, “ladder”) +‎ 高 (taka). The taka changes to daka as an instance of rendaku (連濁).

The term is in reference to the way the central top portion of the 旧字体 (kyūjitai, “old form”, prior to various writing reforms) of the character looks a bit like a ladder. Compare the two forms:

• 髙 as the 旧字体 (kyūjitai, “old form”) and "ladder" version
• 高 as the 新字体 (shinjitai, “new form”)

• IPA^(key): [ha̠ɕiɡo̞da̠ka̠]

はしご高(だか) • (hashigodaka) 

1. a nickname for the 髙 character, a variant of 高

• 口高(くちだか) (kuchidaka)