Words/tune will be in my sublim

[Park 10]

i have used the phrase 'it will be in my sublim' for many years in the context of a tune I do not realise I know until I hear it.in other words it is buried in the back of my mind. it is now beginning to annoy my other half as he thinks that people are bemused by this but dare not say. am I making this up - could it be a local saying from my childhood in Northamptonshire? I am just puzzled and google is no help. thanks