What this suffix does
-kept forms compound adjectives that describe how well or poorly something has been maintained, cared for, or preserved. Well-kept, poorly-kept, ill-kept, badly-kept, meticulously-kept — each compound evaluates the quality of maintenance. The compounds apply to gardens, houses, records, secrets, promises, and any other thing that requires active maintenance to retain its quality. In literary writing -kept compounds are used to characterise both spaces (a well-kept garden says something about its owner) and inner life (a well-kept secret, a poorly-kept promise).