1.
corner; nook; edge
A corner or out-of-the-way spot. An informal, slightly childish variant of 隅 that adds a sense of smallness or coziness.
隅っこ is a casual, diminutive form of 隅 (corner). The っこ suffix adds a sense of smallness and is common in informal speech.
The word has gained wider recognition through the popular San-X character franchise 「すみっコぐらし」(Sumikko Gurashi), which features characters who like to gather in corners.