Error showing Expected Array for VBA to name file name in column

I would like to name Range("A1") as May22 which can be extracted from the filename.

However when the code was executed, error message was triggered: Expected Array.

Sub copyfilename ()

Dim ws As Worksheet
Set ws = Sheet1

Dim fileName As String
Dim columnName As String

fileName = "V:\Finance\Systems-Risk-ERM\OrderToCash\C2C\Corp Credit Control\3. Monthly Combined Aging\2022\May22\Top Segments & Top All_May22.xlsm"

columnName = Split(fileName, "\")

ws.Range("A1").Value = columnName(8)

End Sub

Is there a way around this? Appreciate the help!