bash - Sed into Variable not working properly -

i trying strip except letters , delete letters less 3 characters in bash script... got delete words has 3 characters, other rules not applied. here's i'm using:

name="the man u.n.c.l.e. official 2 2015 henry cavill armie hammer spy movie hd" keyword="$(sed -e 's/ [a-za-z]\{3\} / /g' <<< "$name")" 

desired output is

echo $keyword

shows

the man official henry cavill armie hammer spy movie

any kind of can on appreciated!

try gnu sed:

name="the man u.n.c.l.e. official 2 2015 henry cavill armie hammer spy movie hd" keyword="$(sed -e 's/\b(.{1,2}|[0-9]+)\b/ /g;s/ +/ /g' <<< $name)" echo "${keyword% }" 

output:

 man official henry cavill armie hammer spy movie