mealy-mouthed
Concise Oxford English Dictionary © 2008 Oxford University Press:
mealy-mouthed
▶adjective reluctant to speak frankly.
– origin C16: perh. from Ger. Mehl im Maule behalten, lit. ‘carry meal in the mouth’, i.e. be unstraightforward in speech, or rel. to L. mel ‘honey’.
'mealy-mouthed' also found in these Oxford entries:

